1. Field of the Invention
This invention is in the field of orthopedics and, more particularly, directed to spinal implants.
2. Prior Art
Spinal stabilization is one approach to alleviating chronic back pain caused by displaced disk material or excessive movement of individual vertebrae. Conventional stabilization techniques include fusing two or more vertebrae together to circumvent or immobilize the area of excessive movement. Normally, the vertebral disk material which separates the vertebrae is removed and bone graft material is inserted in the space for interbody fusion. In addition, or in place of, the bone graft material, a spinal implant may be inserted in the intervertebral space.
The conventional surgical approach for stabilization has been posteriorly for ease of access to the spine and to avoid interfering with internal organs and tissue. Usually the implant site is prepared to maintain natural lordosis and to accept a certain sized implant within certain pressure limits. This requires considerable time and skill by the surgeon.
Published U. S. Patent Application, US 2004/0122518 A1, to Rhoda discloses a hollow wedge shaped vertebral implant used in fusing two adjacent vertebrae.
Published U.S. Patent Application, US 2004/0186570 A1, to Rapp discloses a intervertebral implant with upper and lower plates spaced apart by a wedge shaped strut. The plates are open and filled with bone graft material.
U.S. Pat. No. 6,562,074 to Gerber et al issued May 13, 2003 discloses a spinal insert which can be manipulated to adjust the height of the implant through links connected to the upper and lower plates.
U.S. Pat. No. 6,120,506 issued Sep. 19, 2000 to Kohrs et al discloses a lordotic implant and a tap for use in preparing the vertebrae. The implant is designed to be inserted between the non-parallel end plates of adjacent vertebrae and maintain the natural lordotic angle of the spine. This is done through the use of a threaded tapered plug inserted in a tapped hole in the direction required by the lordosis of the spine. The implant is hollow and has radial apertures for accommodating bone graft material.
U.S. Pat. No. 6,015,436 issued Jan. 18, 2000 to Shoenhoeffer discloses a tubular spinal implant. The implant is hollow and has radial apertures for interbody fusion through bone growth material. The device is placed between adjacent vertebrae with the opposite ends of the tube contacting the opposing vertebrae. The opposite ends are threaded together to form the hollow tube.
The prior art devices that incorporate bone graft material provide a solid plug of graft material contacting each adjacent vertebrae at the ends of the plug. A significant amount of time is required for the solid plug to become integrated with spiny ingrowth from the vertebrae.
Therefore, what is needed is an implant that provides quicker fusion and increased reinforcement between the end plates of the adjacent vertebrae.